Fix crashes introduced by heuristically dropping file and directory l…

…isting state nodes

# Background
* 658ba15 implemented heuristically dropping state nodes under flag `--experimental_heuristically_drop_nodes`. Multiple blaze crashes are observed when the flag is applied.
* abb402e enhanced `GraphInconsistencyReceiver` (`GIR` in short) so that it can tolerate inconsistencies introduced by heuristically dropping state nodes regardless of rewinding. This commit also fixes the crash when blaze cannot get file/directory state `depKey`s for symlinks.

# Goal of this commit

Local tests with target `//devtools/blaze/main:blaze` still indicates two other crashes when heuristically dropping state nodes.

1. `SkyFunctionEnvironment#batchPrefetch(true)` could inform `GIR` with `BUILDING_PARENT_FOUND_UNDONE_CHILD` inconsistency which also needs to be tolerated.
2. `AbstractParallelEvaluator#maybeHandleRegisteringNewlyDiscoveredDepsForDoneEntry()` should re-create instead of crash when declared dep is missing.

PiperOrigin-RevId: 504053773
Change-Id: I43e2f90ac3b84a9fbe9e590c90c20db3a94cd54b

src/main/java/com/google/devtools/build/lib/skyframe/NodeDroppingInconsistencyReceiver.java

@@ -61,7 +61,8 @@ public static boolean isExpectedInconsistency(
     if (inconsistency == Inconsistency.RESET_REQUESTED) {
       return otherKeys == null;
     }
-    if (inconsistency == Inconsistency.ALREADY_DECLARED_CHILD_MISSING) {
+    if (inconsistency == Inconsistency.ALREADY_DECLARED_CHILD_MISSING
+        || inconsistency == Inconsistency.BUILDING_PARENT_FOUND_UNDONE_CHILD) {
       // For already declared child missing inconsistency, key is the parent while `otherKeys`
       // are the children (dependency nodes).
       SkyFunctionName expectedStateKeyType =

src/main/java/com/google/devtools/build/lib/skyframe/SkyframeExecutor.java

@@ -3387,6 +3387,7 @@ private <T extends SkyValue> EvaluationResult<T> evaluate(
             .setKeepGoing(keepGoing)
             .setParallelism(numThreads)
             .setEventHandler(eventHandler)
+            .setHeuristicallyDropNodes(heuristicallyDropNodes)
             .build();
     return memoizingEvaluator.evaluate(roots, evaluationContext);
   }

src/main/java/com/google/devtools/build/skyframe/AbstractParallelEvaluator.java

@@ -118,6 +118,8 @@ abstract class AbstractParallelEvaluator {
 
   protected final Cache<SkyKey, SkyKeyComputeState> stateCache = Caffeine.newBuilder().build();
 
+  private final boolean heuristicallyDropNodes;
+
   AbstractParallelEvaluator(
       ProcessableGraph graph,
       Version graphVersion,
@@ -132,7 +134,8 @@ abstract class AbstractParallelEvaluator {
       GraphInconsistencyReceiver graphInconsistencyReceiver,
       QuiescingExecutor executor,
       CycleDetector cycleDetector,
-      boolean mergingSkyframeAnalysisExecutionPhases) {
+      boolean mergingSkyframeAnalysisExecutionPhases,
+      boolean heuristicallyDropNodes) {
     this.graph = graph;
     this.cycleDetector = cycleDetector;
     this.evaluatorContext =
@@ -151,6 +154,7 @@ abstract class AbstractParallelEvaluator {
             () -> new NodeEntryVisitor(executor, progressReceiver, Evaluate::new, stateCache),
             /* mergingSkyframeAnalysisExecutionPhases= */ mergingSkyframeAnalysisExecutionPhases,
             stateCache);
+    this.heuristicallyDropNodes = heuristicallyDropNodes;
   }
 
   /**
@@ -1108,14 +1112,16 @@ private boolean maybeHandleRegisteringNewlyDiscoveredDepsForDoneEntry(
     }
 
     for (SkyKey newDep : newlyAddedNewDeps) {
-      // TODO(b/261019506): When heuristically dropping node is enabled, declared dep might be
-      //  missing and the check below will fail leading to blaze crash.
       NodeEntry depEntry =
-          checkNotNull(
-              newlyAddedNewDepNodes.get().get(newDep),
-              "Missing already declared dep %s (parent=%s)",
-              newDep,
-              skyKey);
+          heuristicallyDropNodes
+              ? getOrRecreateDepEntry(
+                  newDep, newlyAddedNewDepNodes.get(), skyKey, Reason.RDEP_ADDITION)
+              : checkNotNull(
+                  newlyAddedNewDepNodes.get().get(newDep),
+                  "Missing already declared dep %s (parent=%s)",
+                  newDep,
+                  skyKey);
+
       DependencyState triState = depEntry.addReverseDepAndCheckIfDone(skyKey);
       switch (maybeHandleUndoneDepForDoneEntry(entry, depEntry, triState, skyKey, newDep)) {
         case DEP_DONE_SELF_SIGNALLED:
@@ -1140,6 +1146,29 @@ private boolean maybeHandleRegisteringNewlyDiscoveredDepsForDoneEntry(
     return !selfSignalled;
   }
 
+  /**
+   * Returns a {@link NodeEntry} for {@code depKey}.
+   *
+   * <p>If {@code depKey} is present in {@code depEntries}, its corresponding entry is returned.
+   * Otherwise, if the evaluator permits {@link Inconsistency#ALREADY_DECLARED_CHILD_MISSING}, the
+   * entry will be recreated.
+   */
+  private NodeEntry getOrRecreateDepEntry(
+      SkyKey depKey, NodeBatch depEntries, SkyKey requestor, Reason reason)
+      throws InterruptedException {
+    NodeEntry depEntry = depEntries.get(depKey);
+    if (depEntry != null) {
+      return depEntry;
+    }
+
+    ImmutableList<SkyKey> missing = ImmutableList.of(depKey);
+    evaluatorContext
+        .getGraphInconsistencyReceiver()
+        .noteInconsistencyAndMaybeThrow(
+            requestor, missing, Inconsistency.ALREADY_DECLARED_CHILD_MISSING);
+    return checkNotNull(graph.createIfAbsentBatch(requestor, reason, missing).get(depKey), depKey);
+  }
+
   private enum MaybeHandleUndoneDepResult {
     DEP_DONE_SELF_SIGNALLED,
     DEP_DONE_SELF_NOT_SIGNALLED,

src/main/java/com/google/devtools/build/skyframe/EvaluationContext.java

@@ -35,6 +35,7 @@ public class EvaluationContext {
   private final boolean isExecutionPhase;
   private final boolean mergingSkyframeAnalysisExecutionPhases;
   private final UnnecessaryTemporaryStateDropperReceiver unnecessaryTemporaryStateDropperReceiver;
+  private final boolean heuristicallyDropNodes;
 
   protected EvaluationContext(
       int parallelism,
@@ -43,14 +44,16 @@ protected EvaluationContext(
       ExtendedEventHandler eventHandler,
       boolean isExecutionPhase,
       boolean mergingSkyframeAnalysisExecutionPhases,
-      UnnecessaryTemporaryStateDropperReceiver unnecessaryTemporaryStateDropperReceiver) {
+      UnnecessaryTemporaryStateDropperReceiver unnecessaryTemporaryStateDropperReceiver,
+      boolean heuristicallyDropNodes) {
     this.parallelism = parallelism;
     this.executor = executor;
     this.keepGoing = keepGoing;
     this.eventHandler = Preconditions.checkNotNull(eventHandler);
     this.isExecutionPhase = isExecutionPhase;
     this.mergingSkyframeAnalysisExecutionPhases = mergingSkyframeAnalysisExecutionPhases;
     this.unnecessaryTemporaryStateDropperReceiver = unnecessaryTemporaryStateDropperReceiver;
+    this.heuristicallyDropNodes = heuristicallyDropNodes;
   }
 
   public int getParallelism() {
@@ -113,6 +116,10 @@ public UnnecessaryTemporaryStateDropperReceiver getUnnecessaryTemporaryStateDrop
     return unnecessaryTemporaryStateDropperReceiver;
   }
 
+  public boolean getHeuristicallyDropNodes() {
+    return heuristicallyDropNodes;
+  }
+
   public Builder builder() {
     return newBuilder().copyFrom(this);
   }
@@ -131,6 +138,7 @@ public static class Builder {
     protected boolean mergingSkyframeAnalysisExecutionPhases;
     protected UnnecessaryTemporaryStateDropperReceiver unnecessaryTemporaryStateDropperReceiver =
         UnnecessaryTemporaryStateDropperReceiver.NULL;
+    protected boolean heuristicallyDropNodes;
 
     protected Builder() {}
 
@@ -192,6 +200,12 @@ public Builder setUnnecessaryTemporaryStateDropperReceiver(
       return this;
     }
 
+    @CanIgnoreReturnValue
+    public Builder setHeuristicallyDropNodes(boolean heuristicallyDropNodes) {
+      this.heuristicallyDropNodes = heuristicallyDropNodes;
+      return this;
+    }
+
     public EvaluationContext build() {
       return new EvaluationContext(
           parallelism,
@@ -200,7 +214,8 @@ public EvaluationContext build() {
           eventHandler,
           isExecutionPhase,
           mergingSkyframeAnalysisExecutionPhases,
-          unnecessaryTemporaryStateDropperReceiver);
+          unnecessaryTemporaryStateDropperReceiver,
+          heuristicallyDropNodes);
     }
   }
 }

src/main/java/com/google/devtools/build/skyframe/InMemoryMemoizingEvaluator.java

@@ -205,7 +205,8 @@ public <T extends SkyValue> EvaluationResult<T> evaluate(
                                 ParallelEvaluatorErrorClassifier.instance())),
                 new SimpleCycleDetector(),
                 evaluationContext.mergingSkyframeAnalysisExecutionPhases(),
-                evaluationContext.getUnnecessaryTemporaryStateDropperReceiver());
+                evaluationContext.getUnnecessaryTemporaryStateDropperReceiver(),
+                evaluationContext.getHeuristicallyDropNodes());
         result = evaluator.eval(roots);
       }
       return EvaluationResult.<T>builder()

src/main/java/com/google/devtools/build/skyframe/ParallelEvaluator.java

@@ -71,7 +71,8 @@ public ParallelEvaluator(
       QuiescingExecutor executor,
       CycleDetector cycleDetector,
       boolean mergingSkyframeAnalysisExecutionPhases,
-      UnnecessaryTemporaryStateDropperReceiver unnecessaryTemporaryStateDropperReceiver) {
+      UnnecessaryTemporaryStateDropperReceiver unnecessaryTemporaryStateDropperReceiver,
+      boolean heuristicallyDropNodes) {
     super(
         graph,
         graphVersion,
@@ -86,10 +87,46 @@ public ParallelEvaluator(
         graphInconsistencyReceiver,
         executor,
         cycleDetector,
-        mergingSkyframeAnalysisExecutionPhases);
+        mergingSkyframeAnalysisExecutionPhases,
+        heuristicallyDropNodes);
     this.unnecessaryTemporaryStateDropperReceiver = unnecessaryTemporaryStateDropperReceiver;
   }
 
+  public ParallelEvaluator(
+      ProcessableGraph graph,
+      Version graphVersion,
+      Version minimalVersion,
+      ImmutableMap<SkyFunctionName, SkyFunction> skyFunctions,
+      ExtendedEventHandler reporter,
+      NestedSetVisitor.VisitedState emittedEventState,
+      EventFilter storedEventFilter,
+      ErrorInfoManager errorInfoManager,
+      boolean keepGoing,
+      DirtyTrackingProgressReceiver progressReceiver,
+      GraphInconsistencyReceiver graphInconsistencyReceiver,
+      QuiescingExecutor executor,
+      CycleDetector cycleDetector,
+      boolean mergingSkyframeAnalysisExecutionPhases,
+      UnnecessaryTemporaryStateDropperReceiver unnecessaryTemporaryStateDropperReceiver) {
+    this(
+        graph,
+        graphVersion,
+        minimalVersion,
+        skyFunctions,
+        reporter,
+        emittedEventState,
+        storedEventFilter,
+        errorInfoManager,
+        keepGoing,
+        progressReceiver,
+        graphInconsistencyReceiver,
+        executor,
+        cycleDetector,
+        mergingSkyframeAnalysisExecutionPhases,
+        unnecessaryTemporaryStateDropperReceiver,
+        /* heuristicallyDropNodes= */ false);
+  }
+
   private void informProgressReceiverThatValueIsDone(SkyKey key, NodeEntry entry)
       throws InterruptedException {
     if (evaluatorContext.getProgressReceiver() == null) {